91Ó°ÊÓ

Four conformations are possible for cyclohexane: a chair, twist boat, boat, and half chair. Among all the four conformations chair form of cyclohexane is considered a very stable one. Chair conformation of cyclohexane is as follows;

Chair form of cyclohexane

We can say if the relation is up-up, then cis, if down–down relationship, then trans.

If the up-down or down-up relation between the bond, then trans.

The two chair conformation of trans-1-chloro-2-methylcyclohexane are shown as follow;

If we compare both the conformation, it is observed that in 1 st case, chlorine and methyl groups are present in an equatorial position. While in the case of the second structure, both groups are in the axial position, indicating that both groups are in the axial position. It indicates that they show 1, 3 diaxial interaction. Hence stability decreases.

So 1^st structure is stable as compared to the 2^nd one.